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Adequate concentrations of maternal and neonatal thyroid hormones are essential for fetal neural development and play a key part in regulating fetal growth, brain development, and metabolism. Fetal thyroid function begins at 12–14 weeks gestation; however, maternal transfer of thyroid hormones continues until full-term and has a protective role in fetal neurodevelopment until the first few days of life.

The thyroid gland

Thyroid hormone concentrations in newborn babies are affected by neonatal, maternal, and pregnancy-related factors, including maternal thyroid function and iodine status. Congenital hypothyroidism is defined as inadequate thyroid function in newborn infants and is one of the most readily preventable causes of intellectual disability in children.

A world-first University of Sydney study in The Lancet Diabetes and Endocrinology reveals Australian babies born with moderately high concentrations of a hormone called thyroid stimulating hormone (TSH) have a higher risk of poor educational and development outcomes at school age. It suggests that the mother is not consuming enough iodine. This is the first population-based study demonstrating the association between moderately high TSH in infants and their later school age neurodevelopmental outcomes.

Congenital hypothyroidism refers to abnormal thyroid function in newborn infants. Globally, about one in 2000 children are born with congenital hypothyroidism each year and the incidence of subclinical thyroid disease is at least ten times higher than overt thyroid disease. If untreated for several months after birth, severe congenital hypothyroidism can lead to growth failure and permanent intellectual disability.

Screening for congenital hypothyroidism in the first days of life, done usually by testing concentrations of neonatal thyroid-stimulating hormone in baby’s blood, provides an opportunity to identify infants with abnormal thyroid hormone concentrations. In developed countries, newborn screening of TSH levels and early treatment for congenital hypothyroidism has nearly eliminated intellectual disabilities associated with congenital hypothyroidism. Currently, only newborns with TSH concentrations at the 99.95th percentile of the population range, are diagnosed with congenital hypothyroidism and treated with the hormone thyroxine. At this percentile, blood concentration of TSH usually exceeds 20 mU per litre of whole blood.

The researchers found that infants with a neonatal TSH concentration just lower than the cut-off (20 mU/L blood, a near miss) have an increased likelihood of poor neurodevelopmental outcomes at school age. Said another way, the study reveals a gradual increasing risk of poor educational and development outcomes for newborns with increasing TSH concentrations from the 75th to the 99.95th percentile.

“The results showed a clear dose-response association between neonatal thyroid stimulating hormone and risk of scoring below the national minimum standard for numeracy and reading,” said the University of Sydney’s A/Professor Natasha Nassar, the study’s senior author.

“This study can’t prove a cause and effect relationship between thyroid stimulating hormone levels in newborns and educational and development outcomes in school age children, but it suggests an urgent need for prospective studies examining different thyroid hormone thresholds for intervening with thyroxine,” said Dr Bridget Wilcken, Clinical Professor of Paediatrics and Child Health at the Children’s Hospital at Westmead. “Given that thyroxine is a relatively safe medication when indicated and properly monitored, this simple intervention may prevent significant learning and developmental problems in a small group of affected children.”

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Iodine is a naturally occurring mineral that is needed by the thyroid gland in order to synthesize thyroxine, an important hormone that regulates metabolism. In babies and young children, thyroid hormones play a key role in physical and mental development. A deficiency of iodine can lead to learning difficulties and affect physical development and hearing. The recommended dietary intake a day for iodine is 150 micrograms for most adults, but this increases to 220 micrograms during pregnancy and 270 micrograms while breast-feeding, as your baby will take the iodine it needs from you.

The mineral iodine

Iodine deficiency
Because Australian and New Zealand soils are low in iodine, the National Health and Medical Research Council and the New Zealand Ministry of Health recommend that all women who are pregnant, breastfeeding or considering pregnancy, take an iodine supplement. However, it’s best to speak with your doctor before taking a supplement, especially if you have a pre-existing thyroid condition.

Though iodine deficiency is not typically a problem in the United States, as most table salt is enriched with iodine, the American Thyroid Association recommends that all women who are pregnant, breast-feeding, or considering pregnancy take an iodine supplement of 150 micrograms each day. Kelp and seaweed supplements are not recommended as they contain varying amounts of iodine and can even cause toxicity (too much iodine). Again, speak with your doctor first.

The best source of iodine in our diet is seafood. We also get iodine from other foods including milk and vegetables, but the amount varies depending on how these foods are grown and processed. In Australia and New Zealand, all salt used for making bread (apart from organic breads) must now be iodised, so bread has become a source of iodine. 

A study of more than 1000 Canadian mothers and their infants in Journal of Pediatrics found exclusive breastfeeding in the first three months of life provided more protection against an infant becoming overweight at one year of age than either partial breastfeeding or formula feeding. This association is partially explained by the influence breastfeeding has on an infant’s gut microbiome say the researchers. “Breastfeeding is one of the most influential factors in shaping the infant gut microbiome,” says Dr. Meghan Azad.

“Our research showed that partial breastfeeding and exclusive formula feeding were associated with a higher microbial diversity at three months of age, meaning more types of microbes were present in the baby’s gut, as well as an abundance of a group of bacteria called Lachnospiracae, which has been associated with infant overweight,” explains Dr. Anita Kozyrskyj. “We also distinguished between partial breastfeeding mixed with formula versus partial breastfeeding mixed with foods,” adds Dr. Jessica Forbes. “We found that breastfed infants supplemented with formula were at increased risk for becoming overweight at one year of age, and had a different microbiota composition than exclusively breastfed infants; whereas breastfed infants supplemented with complementary foods only (no formula) were similar to exclusively breastfed infants with no increased risk.”

 “These results emphasize the importance of breastfeeding as a possible protective factor against infant overweight by modifying the gut microbiome,” says Azad. “They suggest that improved programs and policies to support exclusive breastfeeding could have a meaningful impact on infant health.”

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Mother’s milk provides the perfect mix of nutrients – carbs, fat, protein, vitamins and minerals – for babies to grow and thrive for the first six months of life. Mother Nature made it sweet so it is very appealing to babies. The sweetness comes from a special sugar called lactose only found in milk. Our human milk has one of the highest concentrations of lactose of any mammal coming in at some 7 grams of lactose per 100 millilitres (3½ fluid ounces) which in household measures is little over ⅓ cup. It is about 1½ times that of cow’s milk. Why so much? One reason is probably to satisfy our fast-growing, energy-hungry, glucose-demanding brain. Scans show that a baby’s brain reaches more than half adult size in the first 90 days of baby’s life.

Breast feeding

Mother’s milk also contains special carbs called oligosaccharides (think of them as prebiotics, foods that friendly bacteria in the large intestine chomp on to thrive).

Human breast milk analysis
Source: The Good Carbs Cookbook

The man who transformed our thinking about the causes of diabetes, cardiovascular disease and cancer was Sir David Barker (physician, biologist and epidemiologist). Caroline Fall and Clive Osmond remind us that Barker’s: “‘fetal programming hypothesis’ challenged the idea that these diseases are explained by bad genes and unhealthy adult lifestyles. Instead, he proposed, their roots lie in the early life environment: ‘The nourishment a baby receives from its mother, and its exposure to infection after birth, determine its susceptibility to chronic disease in later life’. By permanently ‘programming’ the body’s metabolism and growth, they determine the pathologies of old age. His now widely accepted ideas stimulated research into the developmental origins of health and disease. To pull back the modern epidemics of chronic disease we should prioritise the health and nutrition of girls, pregnant women and infants.” And he said this over 20 years ago.

“Maternal nutrition is more important than we ever imagined,” says Prof Jennie Brand-Miller. “Life inside the womb is a critical period for metabolic programming that influences a baby’s cell types, cell numbers, body composition, hormonal feedback, metabolic activity, and appetite. Our food supply and dietary recommendations should be based first and foremost on the needs of pregnant women,” she says. “If we cover them, we automatically cover everyone else. They should not be seen as the exception to the rule (and simply recommended nutritional supplements). We now also know that different patterns of growth have long-term effects on the risk of specific diseases. If growth is restricted, there is a higher risk of abdominal obesity, cardiovascular disease and type 2 diabetes as an adult. Over-nutrition, seen for example in maternal diabetes and obesity, is also linked to increased risk of obesity in adult life. The positive news is that we know that interventions in pregnancy are probably more effective than later interventions. So, we have to give Mum and her unborn baby much greater focus.”

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Improving your own health before conception and providing a healthy environment for your unborn child can go a long way towards ensuring they have the best possible start in life. Here are eight tips from The Low GI Plan for Optimal Pregnancy for improving your health three to six months before conception.

  1. Organise your pre-pregnancy health checks with your doctor. 
  2. Review your medications (including non-prescription medications and supplements) with your doctor. Optimal intakes of iron, folate and iodine is critical. 
  3. If you smoke, do your best to stop. 
  4. Avoid alcohol and perhaps coffee (and other highly caffeinated beverages). 
  5. Ensure your eating habits are healthy. 
  6. Be physically active. 
  7. If you are overweight, improve your diet and activity to achieve gradual weight loss. 
  8. Take folate and iodine supplements 

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Mexican restaurants are popping up all over. They are ideal for low GI choices because they make great use of beans and corn. They also have small portions such as tacos if you just want a light meal. There are usually plenty of gluten-free and vegetarian choices. Menus often include detailed descriptions of dishes so you know exactly what you are getting (and you can always ask). Good options include:

  • Tacos, burritos and quesadillas with mushrooms or vegetables, fish, seafood, pulled pork, beef, and chicken 
  • Salads and salsas of all kinds 
  • Chargrilled corn 
  • Ceviche bowls with tuna, salmon or kingfish 
  • Share plates with grilled octopus, guacamole, corn tamales.